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Springer Series on 35 ATOMIC, OPTICAL, AND PLASMA PHYSICS Springer-Verlag Berlin Heidelberg GmbH ONLINE LIBRARY Physics and Astronomy http://www.springer.de/phys/ Springer Series on ATOMIC, OPTICAL, AND PLASMA PHYSICS The Springer Series on Atomic, Optical, and Plasma Physics covers in a compre hensive manner theory and experiment in the entire field of atoms and molecules and their interaction with electromagnetic radiation. Books in the series provide a rich source of new ideas and techniques with wide applications in fields such as chemistry, materials science, astrophysics, surface science, plasma technology, ad vanced optics, aeronomy, and engineering. Laser physics is a particular connecting theme that has provided much of the continuing impetus for new developments in the field. The purpose of the series is to cover the gap between standard under graduate textbooks and the research literature with emphasis on the fundamental ideas, methods, techniques, and results in the field. 27 Quantum Squeezing By P.D. Drumond and Z. Spicek 28 Atom, Molecule, and Cluster Beams I Basic Theory, Production and Detection of Thermal Energy Beams ByH. Pauly 29 Polarization, Alignment and Orientation in Atomic Collisions By N. Andersen and K. Bartschat 30 Physics of Solid-State Laser Physics By R.C. Powell (Published in the former Series on Atomic, Molecular, and Optical Physics) 31 Plasma Kinetics in Atmospheric Gases By M. Capitelli, C.M. Ferreira, B.F. Gordiets, A.1. Osipov 32 Atom, Molecule, and Cluster Beams II Cluster Beams, Fast and Slow Beams, Accessory Equipment and Applications ByH. Pauly 33 Atom Optics By P. Meystre 34 Laser Physics at Relativistic Intensities By A. V. Borovsky, A.L. Galkin, O.B. Shiryaev, T. Auguste 35 Many-Particle Quantum Dynamics in Atomic and Molecular Fragmentation Editors: J. Ullrich and v.P. Shevelko Series homepage - http://www.springer.de/phys/books/ssaop/ Vols. 1-26 of the former Springer Series on Atoms and Plasmas are listed at the end of the book J. Ullrich v.P. Shevelko (Eds.) Many-Particle Quantum Dynamics in Atomic and Molecular Fragmentation With 179 Figures i Springer Professor Dr. Joachim Ullrich Max-Planck Institut flir Kernphysik Saupfercheckweg 1, 69117 Heidelberg, Germany E-mail: [email protected] Professor Dr. Viatcheslav Shevelko P.N. Lebedev Physical Institute Leninskii prospect 53, 119991 Moscow, Russia E-mail: [email protected] ISSN 1615-5653 ISBN 978-3-642-0526-0 ISBN 978-3-662-08492-2 (eBook) DOI 10.1007/978-3-662-08492-2 Library of Congress Cataloging-in-Publication Data Many-particle quantum dynamics in atomic and molecular fragmentation!). Ullrich, V.P. Shevelko (eds.). p. cm. - (Springer series on atomic, optical, and plasma physics, ISSN 1615-5653 ; 35) Includes bibliographical references and index. 1. Collisions (Atomic physics) 2. Atomic and molecular fragmentation. 3. Many-body problem. 4. Quantum theory. I. Ullrich, ). (Joachim) II. Shevel'ko, V.P. (Viatcheslav Petrovich) III: Series. QC794·6.C6M342003 539·i57-dc21 2003050419 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9,1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. http://www.springer.de © Springer-Verlag Berlin Heidelberg 2003 Originally published by Springer-Verlag Berlin Heidelberg New York in 2003. Softcover reprint ofthe hardcover I st edition 2003 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: Camera-ready copies by the author Final procesing: PTP-Berlin Protago-TeX-Production GmbH, Berlin Cover concept by eStudio Calmar Steinen Cover design: design & production GmbH, Heidelberg Printed on acid-free paper 57!3141!YU -5 4 3 210 Preface This book aims to give a comprehensive view on the present status of a tremendously fast-developing field - the quantum dynamics of fragmenting many-particle Coulomb systems. In striking contrast to the profound theo retical knowledge, achieved from extremely precise experimental results on the static atomic and molecular structure, it was only three years ago when the three-body fundamental dynamical problem of breaking up the hydro gen atom by electron impact was claimed to be solved in a mathematically consistent way. Until now, more "complicated", though still fundamental scenarios, ad dressing the complete fragmentation of the "simplest" many-electron system, the helium atom, under the action of a time-dependent external force, have withstood any consistent theoretical description. Exceptions are the most "trivial" situations where the breakup is induced by the impact of a single real photon or of a virtual photon under a perturbation caused by fast, low charged particle impact. Similarly, the dissociation of the "simplest" molecu Ht lar systems like or HD+, fragmentating in collisions with slow electrons, or the H3 molecule breaking apart into two or three" pieces" as a result of a single laser-photon excitation, establish a major challenge for state-of-the-art theoretical approaches. In the recent past, essentially since less than a decade ago, the field was revolutionized by the invention of advanced, innovative experimental imag ing and projection techniques such as "Reaction Microscopes" - the "bubble chambers of atomic and molecular physics" - or similar projection techniques for fast-moving ion beams. Now these methods enable the measurement of the vector momenta of several fragments (ions, electrons, molecular ions) with unprecedented large solid angles, often reaching a hundred per cent of 47r at extreme precision: Energy resolutions below 1 meV are achieved for slow electrons, while ion momenta are recorded at the /-leV level and below, corresponding to a temperature of a few mK. Often, even "kinematically complete" measurements are feasible, where the complete many-particle fi nal quantum state is mapped and can be visualized, providing the ultimate benchmark for comparison with theory. Imaging techniques, on the one hand, essentially rely on advanced meth ods for precise preparation of the initial quantum state and, thus, are in- VI Preface timately "entangled" and immensely boosted by the present explosion-like advances in the development of cooling techniques: Electron and laser cool ing in storage rings, cold molecular ion sources in combination with small linear traps for cold molecular ions, the use of laser cooling to prepare ultra cold atomic targets or even the Bose-Einstein condensates have just emerged. On the other hand, these techniques have profited tremendously by the avail ability of more sophisticated tools to induce the fragmentation process in a dynamically refined way, to interrogate the breakup time dependence and, maybe in the near future, to even control fragmentation pathways. Among the more sophisticated techniques are intense third-generation synchrotron radiation sources, shorter and shorter, few femto- or even attosecond ("de signed") pulses, pulse-trains and pump-probe arrangements from table-top lasers, upcoming femtosecond VUV free-electron lasers (FEL), as well as in tense beams of highly charged ions providing subattosecond delta pulses to explore inner atomic or molecular dynamics on an ultrashort timescale. In parallel, substantial progress has been achieved in the theoretical treat ment of fragmenting Coulomb systems, driven by conceptual innovations as well as by the dramatic increase of computational capabilities in recent years. For example, the exterior complex scaling method along with the excessive use of massively parallel supercomputers allowed one to solve the fundamental three-particle Coulomb breakup of atomic hydrogen by slow-electron impact mentioned above. Convergent close-coupling calculations, as well as hyper spherical R-matrix methods, the latter combined with semiclassical outgoing waves, were finally able to reliably predict fully differential fragmentation patterns for photo double ionization of the simplest correlated two-electron system, the helium atom. Within the last few years, these methods have been successfully applied to describe double ionization by charged-particle impact at high velocities and the first successful attempts have been un dertaken to implement higher-order contributions at lower velocities. More over, other sophisticated methods were developed or applied in the recent past; among them are the S-matrix approaches to describe the interaction of strong laser fields with atoms, numerical grid methods to directly integrate the Schrodinger equation, hidden crossing techniques at low collision ener gies, time-dependent density functional methods to approach "true" many electron problems, the Green-function theory for N-particle finite systems, as well as semiclassical and classical Monte Carlo approximations. While it is certainly impossible to cover all recent achievements in one single book that, therefore, necessarily has to remain incomplete, we have tried, at least within our personal subjective perspective, to report and re view the most basic methods, techniques and advances as well as on the most significant areas of research by attracting international experts and young researchers. In this book, after a detailed introduction into basic kinematic concepts of atomic and molecular fragmentation reactions in Part I, some of the prominent experimental techniques, underlying concepts, present chal- Preface VII lenges and future prospects are discussed in Part II. Various state-of-the-art theoretical approaches are introduced in Part III followed by different appli cations in Part IV for fragmentation reactions, induced by time-dependent perturbations such as single photons, short-pulse lasers or fast as well as slowly moving electrons and ions. Care was taken to organize the sequence of chapters and each single con tribution in such a way that the nonexpert reader or undergraduate stu dent being familiar with the basic concepts of atomic, molecular and optical physics could be guided in a comprehensive, pedagogical way from the funda mental methods to the most recent techniques and then to the cutting edge of research in the field, experimentally as well as theoretically. At the Uni versity of Heidelberg, this book serves as accompanying material for a newly established Graduate School for Atomic, Molecular and Optical Physics. Heidelberg, Joachim Ullrich May 2003 Viatcheslav Shevelko Contents 1 Kinematics of Atomic and Molecular Fragmentation Reactions V.P. Shevelko and J. Ullrich. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 General Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1 Definitions and Parameters .......................... 2 1.1.2 Fragmentation Reactions for Atomic Targets. . . . . . . . . . . 4 1.2 Particle Kinematics: Fragmentation of Atoms . . . . . . . . . . . . . . . . . 6 1.2.1 Momentum and Energy Conservation Equations in the Nonrelativistic Case. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2.2 Transverse- and Longitudinal-Momentum Balances. . . . . . 9 1.2.3 Fast Ion-Atom Collisions: Small Momentum, Energy, and Mass Transfers . . . . . . . .. 10 1.2.4 Fast Ion-Atom Collisions: Recoil-Ion Momenta. . . . . . . .. 12 1.2.5 Relativistic Case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14 1.3 Ion-Atom Collisions: Illustrative Examples ................... 15 1.3.1 Single-Electron Capture. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15 1.3.2 Target Ionization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18 1.4 Photon-Atom Collisions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20 1.4.1 Photoeffect.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20 1.4.2 Compton Effect .................................... 24 1.5 Particle Kinematics: Fragmentation of Molecules .............. 25 1.5.1 Many-Body Dissociation of Fast Molecular Beams ...... 25 1.5.2 Longitudinal Fragment Velocity Components in the Approximation Zo = 0 . . . . . . . . . . . . . . . . . . . . . . . .. 28 1.5.3 Transverse Fragment Velocity Components in the Approximation of Zero-Beam Extension. . . . . . . . .. 28 1.5.4 Transverse Fragment Velocity Components in the Approximation of Zero-Beam Divergence. . . . . . .. 29 1.5.5 Fragmentation into Two Particles with Equal Masses. . .. 29 References ..................................................... 31 X Contents 2 Recoil-Ion MOlllentulll Spectroscopy and "Reaction Microscopes" R. Moshammer, D. Fischer, H. Kollmus. . . . . . . . . . . . . . . . . . . . . . . . . . .. 33 2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33 2.2 Imaging Spectrometers for Ions ............................. 33 2.2.1 Time Focusing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37 2.2.2 Reconstruction of Momentum Components. . . . . . . . . . . .. 37 2.2.3 Spectrometers with Position-Focusing. . . . . . . . . . . . . . . .. 39 2.2.4 Electric-Field Distortions and Calibration ............. 40 2.3 Target Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41 2.3.1 Supersonic Jets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41 2.3.2 Atomic Traps (MOTRIMS) .... . . . . . . . . . . . . . . . . . . . . .. 44 2.4 Position-Sensitive Detectors .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45 2.4.1 Wedge and Strip Anodes ............................ 45 2.4.2 Delay-Line Anodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 47 2.4.3 Multiple-Hit Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 48 2.5 Imaging Spectrometers for Electrons. . . . . . . . . . . . . . . . . . . . . . . .. 50 2.5.1 Direct Imaging of Electrons. . . . . . . . . . . . . . . . . . . . . . . . .. 51 2.5.2 Reaction Microscopes: Magnetic Guiding of Electrons ... 52 2.5.3 Reconstruction of Electron Momenta. . . . . . . . . . . . . . . . .. 53 2.6 New Developments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55 References ..................................................... 57 3 Multiparticle Illlaging of Fast Molecular Ion Beallls D. Zajfman, D. Schwalm, A. Wolf. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59 3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59 3.2 Basic Concepts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59 3.2.1 Distances and Times: Order of Magnitude. . . . . . . . . . . .. 59 3.2.2 Three-Dimensional vs. Two-Dimensional Imaging. . . . . .. 61 3.3 Detector Concepts and Development. . . . . . . . . . . . . . . . . . . . . . . .. 62 3.3.1 Optical Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 63 3.3.2 Electrical Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 64 3.4 Image Reconstruction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65 3.4.1 Two-Body Fragmentation ........................... 65 3.4.2 Three-Body Channel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67 3.5 Conclusion and Outlook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 68 References ..................................................... 69 4 Neutral-Atolll Illlaging Techniques U. Miiller, H. Helm ............................................. 71 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 71 4.2 Fast-Beam Apparatus ..................................... 72 4.3 Detector Requirements and Specifications .................... 73